1. Technical Field of the Invention
The present invention relates generally to an interchangeable lens which is selectively capable of manual focusing and automatic focusing and a camera for use with such an interchangeable lens. More particularly it relates to an interchangeable lens barrel suited for a type of camera with a built-in motor for focusing whose power is transmitted over a driving shaft to a driven shaft on the interchangeable lens side for focusing an optical system, and a camera equipped therewith.
2. Description of the Prior Art
As an interchangeable lens which is selectively capable of manual focusing and automatic focusing is known by, for example, Japanese utility model laid-open publication Ser. No. Sho-55-105407. In the interchangeable lens disclosed therein there is provided immediately behind the objective lenses a rotary member (body) which rotates about an axis right across an optical axis for receiving a driving force from an automatic focusing mechanism on the camera body side. It is so arranged that a group of lenses for focusing is shifted along the optical axis, as the rotary member is rotated fore and back. Meanwhile, a lens shifting ring which is turned for manual focusing is correlated with a lens focusing mechanism by a clutch mechanism.
This clutch mechanism is so designed that the lens shifting ring for manual focusing is engaged with or disengaged from the lens shifting mechanism for focusing as the lens shifting ring is shifted between two positions on the lens barrel along the lens' optical axis.
With such an interchangeable lens, the lens shifting ring for manual focusing is set at one of the two positions (a first position) when focusing is done automatically. The lens shifting ring for manual focusing is now disengaged from the lens shifting mechanism for the load to be relieved so that automatic focusing operation by the automatic focusing mechanism on the camera body side can be done lightly. When the lens shifting ring is set at the other position (a second position) to thereby engage the lens shifting ring mechanically with the lens shifting mechanism for focusing for manual focusing, the abovementioned rotary member constituting a part of the driving force transmitting system for automatic focusing operation is kept pressed against the driving member on the camera body side, this giving rise to the following inconvenience. It is that when the lens shifting ring is turned for manual focusing, the driving mechanism and the motor on the camera body side for automatic focusing as well as the lens shifting mechanism are driven together so that the response is heavy and the desired light and quick manual focusing operation is interfered with.
Meanwhile, with such a camera it is desired to switch off the automatic focusing circuit when focusing is to be made manually and to have it switched on only when focusing is done automatically. There is, therefore, proposed a system (in e.g. U.S. Pat. No. 4,239,357) in which opening or closing of the abovementioned circuit is interlocked with selection of either of the two states on the interchangeable lens side, namely the state enabling manual focusing and the state enabling automatic focusing by the automatic focusing mechanism on the camera body side, so that opening and closing of such a circuit are done automatically according to manual-automatic change-over for focusing operation. In this system, however, the detecting member for detecting the state selected on the interchangeable lens side is located in a space specially provided in or in the vicinity of the camera body interchangeable lens barrel contact face (the so-called "mount face") and this gives rise to the following inconveniences.
First, there is little place to spare in the vicinity of the mount face of the camera body where iris controlling mechanism, iris information transmitting mechanism, etc. are incorporated. When, nevertheless, a camera is desired to be with a built-in mechanism for automatic focusing, it is necessary to provide the abovementioned detecting member in addition to the driving member for transmission of the output from the automatic focusing mechanism to the interchangeable lens side, this resulting in further limiting the spaces for the abovementioned members to be arranged on the mount face. Hence, according to the abovementioned system, the detecting member is to be located on the mount face together with the driving member, hence required is changing positions of other existing members, etc., and it means a drawback of the degree of freedom of design being affected rather badly.